Integration of reservoir simulation with time-lapse seismic modelling

Ying Zou, Laurence R. Bentley, Laurence R. Lines

Time-lapse seismic modelling was conducted for the Pikes Peak heavy oilfield using the results from a reservoir simulation model. Cyclical steam stimulation (CSS) started in 1981 and continues to the present. A flow simulation model was constructed for the region around a seismic profile that was conducted in 1991 and repeated in 2000. The simulator was run from the start of production in 1981 through 2000. The porosity, saturation, pressure, and temperature were extracted from the reservoir zone from the flow simulator for the pre-production condition and at the times of the 1991 and 2000 surveys. The seismic response of the reservoir was computed using a fluid substitution procedure and forward modelling. Comparing the results of these three times indicated that the gas saturation changes caused the largest change in the simulated seismic response. Seismic difference sections showed that thick zones of gas saturation caused changes in reflection from the tops and bottoms of the reservoir as well as differences deeper in the section due to time delays caused by lower velocity within the reservoir zone. Thin zones of gas caused reflection amplitude differences, but not time delay differences. Temperature and pressure were also correlated with seismic changes, but not as strongly as the gas saturation. However, the changes in the moduli with effective stress changes have not yet been incorporated in the rock physics model. In the future, the simulated seismic response changes will be compared to the measured seismic response changes, and the reservoir simulation parameters will be adjusted to match both the production history and the seismic history.